The term “concentrated photovoltaics” (CPV) is confusing, even to many in the solar industry. And no wonder – the term is an umbrella one that includes widely varying technologies. To make matters worse, it is often confused with concentrated solar power (CSP) – or solar thermal – which is another animal altogether.
Then there’s HyperSolar’s breakthrough technology – although technically labeled a low-concentration photovoltaic technology (LCPV) – it bears little resemblance to other products in this space. The HyperSolar technology is so different, in fact, that we like to think of it as redefining CPV.
Because of the unique nature of the HyperSolar technology, we believe it has the potential to revolutionize the economics of solar, allowing solar not only to reach – but exceed – grid parity by transforming the way that solar energy is produced, improving efficiency and driving down costs.
But in order to understand HyperSolar, it is important to understand what it is not. First, it is not traditional solar.
That said, however, the HyperSolar technology is unique in the CPV space because – unlike other CPV technologies – it can be used with traditional solar: It requires no major module modifications. Thus it can be implemented on a large scale and at a low cost – the two primary requisites of a transformative technology.
The problem with traditional solar is the limited efficiency of silicon solar cells. The average conversion efficiency of the traditional silicon solar cell is only about 15 percent, which means that only a fraction of the sun’s energy is converted into energy. What’s more, the silicon cell appears to be reaching its theoretical limit of efficiency.
To get around this limitation, solar innovators have turned to CPV to concentrate the power of the sun, thus allowing the use of fewer expensive cells. But that’s where the similarity among CPV technologies ends.
High-concentration photovoltaics (HCPV) uses optical devices such as dish reflectors to magnify the power of the sun by 100 times or more (according to a definition by SolFocus, an HCPV leader). Because HCPV installations are essentially telescopes, their narrow acceptance angles mean that they “see” only a small part of the sky and thus require mechanical tracking devices to follow the path of the sun.
HCPV installations – which typically use high-performance, high-cost, multi-junction cells rather than silicon cells – have achieved outputs that are double that of traditional solar arrays, but their widespread deployment is limited by their bulk, their reliance on failure-prone tracking devices and the fact that they are only practical in high-solar resource regions due to their narrow acceptance angles.
A number of large and utility-scale HCPV installations have recently been built or are now under construction, which has led some industry analysts to predict a bright future for the role of HCPV in meeting the world’s energy needs. But others are skeptical that HCPV will ever be able to compete with traditional solar because of its expense and its geographical limitations.
A report on CPV recently issued by Greentech Media predicts, for example, that new utility-scale HCPV installations around the globe will grow from under 5 megawatts in 2010 to more than 1,000 megawatts by 2015. But that pales in comparison with the annual installation of traditional, non-concentrated photovoltaics, which was more than 13,000 megawatts in 2010 alone.
At the other end of the spectrum is LCPV, in which the magnification ratio is less than 10, according to the SolFocus definition. LCPV is typically employed with traditional silicon cells. Although LCPV has a broader range of applications than HCPV, it also produces less power. In addition, with the exception of very-low-concentration PV, LCPV also requires some form of tracking.
An example is the LCPV module now under development by California-based SunPower, the nation’s second-largest solar cell and module maker. According to industry analysts, SunPower’s Alpha-2 LCPV system uses mirror-module pairs (called “blades” by SunPower) mounted on single-axis trackers. The company has installed a version of its system at the Sandia National Laboratory in New Mexico.
Similarly, Solaria’s LCPV product is also designed for use with solar tracking systems, which adds to the initial expense as well as to the maintenance costs. Also – unlike HyperSolar’s technology, which can be used with the standard solar cells produced by the majority of cell manufacturers – the Solaria product uses its own solar cell technology, not industry-standard silicon cells.
To confuse matters even further, CSP – which is not a photovoltaic technology – uses mirrors or lenses to heat water in order to create steam, which ultimately drives a steam turbine that generates electricity.
So where does the HyperSolar technology fit in?
Although the HyperSolar technology is categorized as an LCPV technology, it really falls into its own niche for a number of reasons, including: 1) it uses micro-concentrators rather than bulky lenses or optical devices; 2) it requires no tracking devices; 3) it can be used in low-solar-resource regions; and 4) it can be used with the standard solar cells produced by the majority of cell manufacturers.
HyperSolar’s technology thus gives module makers the ability to compete with HCPV technologies in the efficiency game by reducing the amount of expensive silicon or other semiconductor material required to produce the same amount of electricity, but it does not require direct sunlight or modifications such as bulky optical elements and failure-prone tracking devices.
HyperSolar’s ability to concentrate the power of the sun is based on four key photonics innovations:
• Micro-concentrators – A matrix of small, highly efficient solar concentrators is used to collect sunlight throughout the day from a wide range of angles, thus eliminating the need for bulky tracking devices.
• Photonics light routing – A solid-state photonics network underneath the micro-concentrators transports light from collection points at the surface of the top sheet to concentrated output sites at the bottom.
• Photonics light separation – The photonics network increases efficiency by separating sunlight into spectrum ranges that are routed to solar cells using semiconductor materials that operate in narrow, highly efficient spectral bands.
• Photonics thermal management – The heat from the unused portions of the solar spectrum is filtered out, thus avoiding overheating, which can degrade the cell performance.
HyperSolar is now being developed for use with silicon cells. The technology takes the form of an acrylic top layer that has been demonstrated to increase the power output of a cell by 300 percent (although HyperSolar believes that 400 percent will eventually be achieved), which translates into 66 percent fewer expensive cells needed to convert the same amount of sunlight (see Figure 1). This increase in power output is accomplished by magnifying the sun 3x with the HyperSolar concentrator.
HyperSolar plans to license its technology, manufacturing processes and know-how to module manufacturers, thus reducing costs, product development time and time-to-market, while increasing flexibility and responsiveness. The beauty of the HyperSolar technology is that it will allow the traditional solar industry to scale up without any significant capital investment in new manufacturing protocols.
These differences are what account for HyperSolar’s far-reaching potential. HyperSolar believes its technology has the power to transform solar, making low-cost solar available to the world. In short, we believe HyperSolar is redefining CPV.
About the Author
Tim Young is president and CEO of HyperSolar, whose mission it is to make solar affordable for all. He has more than 15 years’ experience in marketing and management, bringing several new products to market. He holds a B.A. in communications from Pepperdine University.
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